RU2387031C1 - Reactimetre adjustment method - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: reactimetre adjustment method consists in carrying out subsequent operations. First, there performed is discrimination of current pulses of fission chamber above level of high-frequency interference; then there determined is neutron flow density up to the transition level of counting channel to current level; there determined are readings of counting and current channels of reactimetre during transition process and neutron flow density is increased above transition level. After that neuron flow density is decreased below the above level, and by determining the counting channel readings, current value is calculated and compensation of false currents of fission chamber is performed.

EFFECT: invention allows decreasing measurement errors in transient operating modes of reactimetre and increasing adjustment accuracy.

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Description

The invention relates to the field of reactor measurements and can be used in monitoring and control systems of nuclear reactors.

A known method of adjusting the current channel of a reactimeter by compensating for false currents of the fission chamber (E.K. Malyshev, Yu.B. Zasadych, S. A. Stabrovsky. Gas-discharge detectors for monitoring nuclear reactors, M. Energoatomizdat, 1991, p. 46-54; RU patent No. 2076339, publ. 1997). The method includes applying voltage to the working and additional volumes of the division chamber, adding currents from the working and additional volumes.

The disadvantage of this method is the presence of a false output signal, the presence of which reduces the dynamic range of the camera due to a violation of the linear relationship "neutron flux - camera current", caused mainly by the camera current from beta and gamma-active fission products that accumulate in (uranium-containing ) the working section of the chamber in the process of irradiation with neutrons. This current depends on the magnitude of the neutron flux, the duration of exposure and the duration of exposure after irradiation.

A known method of adjusting the reactimeter by discriminating the level of current pulses of the fission chamber. The method is implemented using the device described in patent RU No. 2193245, publ. 11/20/2002. The method includes limiting the influence of high-frequency noise by introducing discrimination of the amplified pulsed signal of the division camera. In this case, the signal from the discriminator is proportional to the value of the neutron flux density.

The disadvantage of this method is the low accuracy of the measurements. The increased error of the reactimeter in the transition mode from one channel to another is due to the different sensitivity level of the current and counting channels of the reactimeter.

The objective of the invention is to provide a method for adjusting a reactimeter with improved parameters.

As a result of solving this problem, a technical result is achieved, consisting in reducing the measurement error in transient modes of the reactimeter, which, in turn, will increase the accuracy of the method.

The problem is solved in that in the known method of adjustment, which includes discrimination of the pulses of the current of the fission chamber above the level of high-frequency interference, in accordance with the proposed technical solution, the neutron flux density is set to the level of transition of the counting channel to the current channel, the readings of the counting and current channels of the reactimeter are determined at the moment transition, increase the neutron flux density above the transition level, and then reduce the neutron flux density below the specified level and, determining the readings deleterious channel calculated current value and produce false compensation currents fission chamber.

A distinctive feature of the proposed technical solution is as follows.

The influence of false currents of the fission chamber on the current, which is proportional to the neutron flux density, leads to a decrease in the sensitivity of the current channel, while the sensitivity of the counting channel remains the same. To eliminate this effect and increase the sensitivity of the current channel, the neutron flux density is set to the level of transition of the counting channel to the current channel and the current value A ₁ in the current channel of the reactimeter and the count value N ₁ in the counting channel are determined. Then, the neutron flux density is reduced to a level at which the readings N _{2 of the} counting channel are less than N ₁ , the calculated value of the current value A _{2 of the} current channel A ₂ is determined as A ₂ = N ₂ · A ₁ / N ₁ . Compensation of the current channel signal to the calculated value allows to restore the sensitivity of the current channel at the counting level and the transition from one channel to another does not increase the measurement error in transient modes of the reactimeter.

The drawing shows a diagram of a device for implementing the method according to the claimed technical solution.

To implement the method, the reagent meter contains an ionization pulse-current chamber 1, a current channel 2 and a counting channel 3. The current channel consists of a current generator 4, an electrometric amplifier 5, and a converter 6 of the amplifier signal to code. The counting channel consists of a series-connected spectrometric amplifier 7, discriminator 8, transducer count-code 9, while the transducers 6 and 9 are connected to the highway, to which a control and indication device 10 is also connected.

The adjustment of the reactimeter is as follows.

At fission chamber 1, a neutron flux of a density is created at which the load of the counting channel is (1 ÷ 1.5) · 10 ⁶ pulses / s for a given value of the discrimination level on the discriminator 8. The magnitude of the discrimination is 25-30% of the nominal value of the amplified pulse . The current A ₁ and the count N _{1 of} the division chamber are determined according to the indications of the indicating device 10. After the chamber is operated in flows greater than those indicated, the neutron flux is reduced to a level at which the readings N _{2 of the} counting channel 3 are lower than N ₁ , but switching to the current channel , since the transition from the current channel 2 to the pulse channel is below the level of 10 ⁶ impulses / s. The calculated values of the readings of the current channel A ₂ are determined as A ₂ = N ₂ · A ₁ / N ₁ .

Changing the amount of current from the generator 4, set the calculated value of the current And ₂ . This ensures the same sensitivity at the moment of transition from the current channel to the counting channel, which ensures a decrease in the measurement error in transient modes of the reactimeter, which, in turn, leads to an increase in the accuracy of the method.

Claims (1)

A method for adjusting a reactimeter, including discrimination of current pulses of the fission chamber above the level of high-frequency interference, characterized in that the neutron flux density is set to the transition level of the counting channel to the current channel, the readings of the counting and current channels of the reactimeter at the moment of transition are determined, and the neutron flux density is increased above the transition level and then reduce the neutron flux density below the specified level and, determining the readings of the counting channel, calculate the current value and compensate for zhnyh fission chamber currents.

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